We have been using an open source WordPress platform with the Graphene theme by Syahir Hakim. The package is completely free and GNU licensed which makes it very popular. It is estimated that more then 20,000 sites use the Graphene theme.
We chose the Graphene theme as it was much more flexible and could be configured in many ways. Early on we used a 3 column format before returning to a single column with more content on the footer.
Graphene 2 has been designed to be responsive which is ideal for mobile users. Instead of a hard coded side, now the site adapts to the screen dimensions of the user, even in portrait mode.
The theme has 12 steps which affords 3 for the sidebar and 9 for the main content window. This can be scaled as desired.